This invention relates to improvements in picks for picking up the sound from musical instruments and converting that sound into an electrical signal, otherwise known as a pick-up. (humbucker guitar pick-ups).
A single-coil pick-up consists of a magnet with a coil around it or a number of magnets with a coil around them.
1950's design type humbucker pick-ups consist of either a flat bar magnet with pole pieces that are magnetic flux conductors (ie ferrous screws or slugs) placed at right angles to the magnet, on each end of the bar magnet (on the south pole and on the north pole of the magnet, bringing a south pole & a north pole up to the strings). There is a coil around the pole pieces on the south pole and a coil around the pole pieces on the north pole. These coils are connected out-of-phase thus canceling electrical noise; they are also magnetically out-of-phase which puts the signal generated from the strings “string-signal”, back in-phase.
Another way is the double humbucker where two single-coil pick-ups with magnets through the centers of their coils, are placed right next to each other side by side, one with the south poles facing the strings and one with the north poles facing the strings. Again the coils are wired out-of-phase thus canceling electrical noise but not the string-signal, in the same way as the pick-up described above.
The split humbucking configuration type pick-up like that seen on some base guitars, consists of two pick-ups in one. One half is placed under the E and A strings, the other half under the D and G strings. The two halves are wired out-of-phase (180 degrees ) to cancel electrical noise.
There are some relatively new humbucker pick-ups using an “EMF-coil” eg a coil that is designed and situated as to pickup electro magnetic field waves EMF (hum) and not the “string-signal”, signals produced by the strings only. The “EMF-coil” is placed next to a “signal-coil” eg a coil that is designed to pickup both string-signal and EMF (hum).
One type, the “active isolation blocking” type humbucker pick-up, consists of an EMF-coil next to a signal-coil and two pre-amplifiers or buffers. The signal from the EMF-coil is fed to one pre-amplifier and the signal from the signal-coil is fed to the other pre-amplifier, then the output of the two pre-amplifiers is mixed together out-of-phase thus canceling the electrical noise.
Another type, the “passive isolation blocking” type humbucker pick-up, consists of an EMF-coil next to a signal-coil. The EMF-coil can be wired out-of-phase, in parallel or in series acting as a noise suppressive inductance or choke, in series or parallel with the signal-coil, as well as an out-of-phase electrical noise generator to reduce electrical noise.
The disadvantages and problems with all of these pick-ups are as follows:
An electro magnetic field “EMF” is generated by anything and everything electrical.
The disadvantage with a single-coil pick-up by itself is that electro magnetic field waves cutting across the pick-up's coil create electrical noise in the output of the pick-up.
The disadvantage with split humbucking configuration type pick-ups is that they will not work on six-string guitars because the strings are too close together. On a bass guitar there is not much interaction between the two halves, ie the strings over one half will not produce much of a signal in the other half, causing induction loading & some cancellation of harmonics.
The disadvantage with 1950s design type humbucker pick-ups & double humbucker type pick-ups is that unlike single-coil pick-ups where the signal is picked up off the string from a single point, incorporating all of the harmonics. These humbucker pick-ups, pick up the signal over the length of the string where the magnetic field extends from one pole piece or magnet to the other. As the harmonics are out-of-phase at these two points they are suppressed dulling the sound. (anti-nodes & nodes problems)
The disadvantage with humbucking with passive isolation blocking is that EMF-coils pick up EMF & cancel hum & noise, but do not pick up much signal from the string. Any signal they do pick up from the string is out of phase to the signal coming from the signal-coil. To the signal coming from the string or the signal-coil, the EMF-coil is a loading inductance and affects the frequency response & dulls the sound. It is also difficult to create a low resistance/low inductance EMF-coil with the same output as a signal-coil with magnets.
The disadvantage with humbucker pick-ups that use active isolation blocking with pre-amplifiers or buffers is that pre-amplifiers generate noise and batteries or power supplies are needed; there is also the problem of matching the resonance of coils and the problems associated with the amplification or presence of an out-of-phase string-signal.
Another problem with both passive and active isolation blocking is that a ferrous metal plate placed between the two coils is necessary to isolate the EMF-coil from the signal-coil. This plate strengthens the magnetic flux and pulls on the guitar strings stopping them from sustaining. In pick-ups with separate magnets under each string the flux varies creating a shape & pattern. When a string is played and bent, it moves through the flux pattern, changing the tone of the note. This plate also changes the shape of the magnetic flux making the flux more constant over and across the top of the pick-up, thus reducing the change in tone as strings are bent.